C# Int Array

Int arrays are common. They store many integer values. And these values can be used in many ways. This introductory material covers int arrays, showing declarations, assignments, elements, loops and methods.

Example 1

This first example shows how you can declare int arrays in four different ways. The first three arrays declared below are declared on single lines, while the fourth array is declared by individual assignment of the elements.

These C# examples use int arrays. They initialize, assign and loop over elements.

Program that uses int arrays [C#]

using System;

class Program
{
    static void Main()
    {
	int[] arr1 = new int[] { 3, 4, 5 }; // Declare int array
	int[] arr2 = { 3, 4, 5 };           // Another
	var arr3 = new int[] { 3, 4, 5 };   // Another

	int[] arr4 = new int[3];            // Declare int array of zeros
	arr4[0] = 3;
	arr4[1] = 4;
	arr4[2] = 5;

	if (arr1[0] == arr2[0] &&
	    arr1[0] == arr3[0] &&
	    arr1[0] == arr4[0])
	{
	    Console.WriteLine("First elements are the same");
	}
    }
}

Output

First elements are the same

Description. In the above example, the message will be written to the console because the first element of each array is identical in value. Note that the first array element is at index 0. This is true in C# but not in VB.NET.

Loop example

Here we see how you can use int arrays in loops. The example shows the foreach loop, which has simpler syntax, and the for loop, which gives you more control and possibly greater performance.

Program that uses int arrays in for loop [C#]

using System;

class Program
{
    static void Main()
    {
	// Loop over array of integers.
	foreach (int id in GetEmployeeIds())
	{
	    Console.WriteLine(id);
	}
	// Loop over array of integers with for.
	int[] employees = GetEmployeeIds();
	for (int i = 0; i < employees.Length; i++)
	{
	    Console.WriteLine(employees[i]);
	}
    }

    /// <summary>
    /// Returns an array of integers.
    /// </summary>
    static int[] GetEmployeeIds()
    {
	int[] employees = new int[5];
	employees[0] = 1;
	employees[1] = 3;
	employees[2] = 5;
	employees[3] = 7;
	employees[4] = 8;
	return employees;
    }
}

Output

1
3
5
7
8
1
3
5
7
8

Description. The Main method calls the GetEmployeeIds() method twice. The first time it calls the method, the ints in the int array are looped over with foreach. The values are written to the screen.

Int array method. The method GetEmployeeIds shows how you can return an int[] array from a method in C#. You never have to free or deallocate the memory for the int array result. It is garbage-collected.

Class example

Here we see how you can use int arrays in your object-oriented program design. The Employee class here stores an internal reference to an int array at the class level. This means it can modify the int array easily and separately.

Example program that uses int array class [C#]

using System;

class Program
{
    static void Main()
    {
	// Declare new int array
	int[] teams = new int[3];
	teams[0] = 1;
	teams[1] = 2;
	teams[2] = 3;

	// New employee that stores int array reference
	Employee employee = new Employee(teams);

	// Loop through each int in employee's class
	foreach (int team in employee.Teams)
	{
	    Console.WriteLine(team);
	}
    }
}

/// <summary>
/// Stores an employee and his teams.
/// </summary>
class Employee
{
    /// <summary>
    /// Int array reference at class level.
    /// </summary>
    int[] _teams;

    /// <summary>
    /// Create new employee.
    /// </summary>
    /// <param name="teams">Teams the employee is in.</param>
    public Employee(int[] teams)
    {
	_teams = teams;
    }

    /// <summary>
    /// Get array of teams.
    /// </summary>
    public int[] Teams
    {
	get
	{
	    return _teams;
	}
    }
}

Output

1
2
3

Description. In the Main method, the code initializes a new int array with three elements. This stores the team numbers that the employee belongs to. The int array here exists only in one place.

Constructor. The Employee constructor accepts a reference to an int array. It then assigns this reference to the local reference at the class level. No element copying is done, making this code fast. Finally, the example has a Teams property that allows external code to get the reference to the int array.

Reference types

An array in the C# language is a reference type, which means it refers to another object and doesn't contain the raw data. You can copy the elements and assign them to a reference.

Performance

Here we note that the array elements in an int array are stored together. Therefore, using an int array is much faster than a LinkedList or ArrayList of ints when looping over the values. If you have to reallocate your int[] with Array.Resize, using List may be faster.

Summary

Here we saw how you can use int arrays in your C# program. We saw how you can declare int arrays in several different ways, and then test individual elements. Int arrays can also be used as parameters and return values.